lecture 6sf - Water is a good solvent for many substances....

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Water is a good solvent for many substances. When ionic substances dissolve in water, their ionic lattices (arrangement of positive and negative ions in three dimensions) breaks down, and the individual ions attach on to the water molecules. This happens since water is polar (has a + and - end). Positive ions attach to the negative end of the water molecule, and negative ions attach to the positive end of the water molecule. This is called ion-dipole attraction, and will be discussed in more detail in later chapters. negative ion attached to positive ion attached to + end of water molecule - end of water molecule When ionic substances dissolve in water, the process is called dissociation. NaCl(s) → Na + (aq) + Cl - (aq) MgCl 2 (s) → Mg 2+ (aq) + 2Cl - (aq) Na 2 SO 4 (s) → 2Na + (aq) + SO 4 2- (aq) Strong and Weak Electrolytes Strong electrolytes are solutions which are good conductors of electricity. Strong electrolytes are solutions which exist completely in the form of ions in aqueous solutions Ionic substances, such as in the dissociation examples above, are all strong electrolytes. Weak electrolytes are substances which are poor (but not zero) electrolytes. They are substances which partially convert into ions in aqueous solutions. However, most of the substance remains in molecular form. Most of the weak electrolytes that we will study are either weak acids or weak bases. Weak acids only partially produce H + ions in water, and weak bases only partially produce OH - ions in water.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Strong and Weak Acids Acids are substances which produce H + ions in aqueous solution. Strong acids completely ionize in aqueous solution to produce H + ions and a negative ion The most important strong acids are hydrochloric acid, sulfuric acid, and nitric acid. All of these exist almost 100% as ions in aqueous solution. Hydrochloric acid HCl → H + (aq) + Cl - (aq) Sulfuric acid H 2 SO 4 → H + (aq) + HSO 4 - (aq) Nitric acid HNO 3 → H + (aq) + NO 3 - (aq) Weak acids only partially ionize into H + and negative ions. Acetic acid is an example of a weak electrolyte. CH 3 COOH H + (aq) + CH 3 COO - (aq) The double arrow, , indicates a state of equilibrium, meaning only a partial amount of the reaction occurs. Equilibrium will be studied in much more detail in future chapters. For acetic acid, only about 1% ionizes to reach equilibrium. In the above example, we represented acetic acid with a condensed structural formula,
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 9

lecture 6sf - Water is a good solvent for many substances....

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online